Layers of the Abdominal Wall – Overview

Do not fear the pelvic floor—although this topic is popular amongst examiners and seems to be complicated at first glance, there is no need for fear. Here, you get a compact overview and learn everything you need to know about the pelvic floor, the abdominal wall and the inguinal canal.

00:01
No we're going to spend a moment to understand
the layering of the abdominal wall.
00:06
And we're going concentrate away from where we
have our vertically oriented muscle andfocus more on the anterolateral portion
of how the abdominal wall is layered.
00:18
First we're going to have the skin and we see
in the illustration here. For example, we see theskin. We will then have two components that make
up superficial fascia. The more superficialcomponent of the fascia is this area here shown
in yellow. This is Camper's fascia,also referred to as the fatty layer. The amount
of adipose tissue is variable. It will depend onthe nutritional status of the individual. The
deepest portion of the superficial fasciais hard to visualize in this illustration.
But this is going to be Scarpa's fascia,also referred to as membranous fascia and that
it is this first dark line that we see herejust underneath the yellow layer representing
Camper's. And it will cross over the midlineand continue on to the opposite side over to the
flat muscles that are found on the more lateralaspects of your abdominal wall. The muscle layers,
and again we're looking at the anterolateralflat muscles, would include the external
abdominal oblique, the internal abdominal oblique,and we also have our transversus abdominis. In
this view we can see the external abdominal obliquewith its fibers running down and in. This slide
will demonstrate the other two muscle layers.
01:55
Here is the cut edge of the external abdominal
oblique along the rib cage. We also havethe cut edge and reflection here of the internal
abdominal oblique which would lie deep to your external.
02:14
And then this demonstrates the deepest flat muscle
layer which would be your transversus abdominis.
02:23
Over here on the other side, we can still see
those same components. External abdominal oblique.
02:31
This is the internal abdominal oblique being
reflected laterally. And then running deep to thatis the transversus abdominis.
02:42
Layers deep to the muscle layers include the
transversalis fascia, the extraperitoneal layer,as well as the parietal peritoneum. Based on how
this illustration is presented, we are going toconcentrate more underneath the rectus abdominis.
But these three components extend laterally as well.
03:07
So what we see here is the transversalis fascia.
This is the fascia that runs on the deep surfaceof the transversus abdominis. What we cannot see
here is just deep to the transversalis fasciawe'll have a thin layer called the extraperitoneal
layer. And there is variable amounts of fatthat can be detected here. And immediately deep
to the extraperitoneal layer, you'll have theparietal peritoneum which is lining the abdominal
cavity. Once you go through the parietal peritoneumyou are then within the peritoneal cavity and
you can see the suspended abdominal viscerawithin the peritoneal cavity.
03:54
It's also worthwhile to understand the dermatomal
pattern to the anterolateral abdominal wall.
04:05
Some key reference points here to help you kind
of understand the levels that are involvedwould be the nipple, the umbilicus
and then your inguinal region.
04:19
These help you identify where T5 lies. So this
area of skin is going to be innervated by theanterior ramus of the fifth thoracic spinal nerve.
That will be just inferior to the level of the nipple.
04:34
T10. This will lie at the level of the umbilicus.
And then lastly the L1 level will lie immediatelyabove the inguinal ligament which would run from
your anterior superior iliac spine down to thepubic tubercle. The inguinal ligament is the
inferior margin of the aponeurosis of theexternal abdominal oblique. An example of how
this might be useful clinically would be witha pregnant women who's undergoing child birth.
She may want to lessen the pain that's associatedwith this life event. And when they administer
the epidural, the physician will want to make surethat the skin is deadened from T10 inferiorly.
And that there is a deadening of the skin bilaterally.
05:35
And if there is, the anaesthetic is going
to be effective in alleviating the pain.
05:44
The inguinal canal is an area shown deep to the
aponeurosis of the external abdominal oblique here.
05:55
It does form the inguinal ligament which would
be running right along here. Coming from theanterior superior iliac spine down to attach to
the pubic tubercle. This is thesuperficial inguinal ring which is an opening then
within the aponeurosis of the external abdominal oblique.
06:16
The inguinal canal transmits two major structures.
The spermatic cord in the male, and then it alsotransmits a supporting ligament of the uterus
in women referred to as the round ligament.
06:33
There are certainly some other structures that
are transmitted but for this overview presentationthis will suffice for now. This now brings us to
the summary slide for we can identify the keytake home messages. First, is the rectus abdominis
defines the linea alba, linea semilunaris,and the tendinous intersection. The abdomen is
divided into a 4 quadrant and a 9 regionpattern. Referred pain by derivatives of the
foregut, midgut and hindgut is to the epigastric,umbilical and pubic regions respectively. Inferior
margins of the rib cage, lumbar vertebrae,superior pelvis structures, and muscles are
major elements that define the abdominal wall.
07:24
Layers of the abdominal wall more laterally would
be the skin, the fascia to include Camper's fascia,Scarpa's fascia. Your three flat muscles, external
abdominal oblique, internal abdominal oblique,and then your transversus abdominis. The transversalis
fascia, the extraperitoneal layer and then lastlywe would have our parietal peritoneum. Dermatomal
levels T6, T10 and L1 correspond to the nipple,umbilicus and inguinal regions, respectively.
The inguinal canal transmits the spermatic cordin the male and the round ligament in the female.
Thank you for joining me on this lecture,on an overview of the abdominal wall.

About the Lecture

The lecture Layers of the Abdominal Wall – Overview by Craig Canby, PhD is from the course Abdominal Wall.

Included Quiz Questions

What is the dermatomal level of the umbilicus?

T10

T6

T8

L12

L1

What muscle belongs to the vertical muscle group of the anterolateral abdominal wall?

Rectus abdominis muscle

External abdominal oblique muscle

Internal abdominal oblique muscle

Transversus abdominis muscle

Psoas major

What layer of the abdominal wall lies immediately beneath the transversus abdominis muscle?

Transversalis fascia

Extraperitoneum

Parietal peritoneum

Internal abdominal oblique muscle

Scarpa's fascia

What are the layers of superficial fascia in the abdomen?

Camper’s and Scarpa's fascia

Deep cervical fascia

Superficial cervical fascia

Fascia lata

Crural fascia

Which of the following is a fatty layer?

Camper’s fascia

Scarpa's fascia

Fascia lata

Crural fascia

Deep cervical fascia

Author of lecture Layers of the Abdominal Wall – Overview

Craig Canby, PhD

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